<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>
	<style>
		*{
			margin:0;
			padding: 0;
		}
		div {
			height: 200px;
			background: pink;
			margin-bottom: 10px;
			display: none;
		}
	</style>
	<script>
		window.onload = function(){
			// console.log(666);
			document.getElementById("btn").onclick =function(){
				//1.展示
					var divs = document.getElementsByTagName("div");
				//2.追加
				 for (var i= 0;i <divs.length;i++) {
				 	divs[i].style.display = 'block';
				 	divs[i].innerText = '一段追加内容';
				 }
			}
		}
	</script>
</head>
<body>
	<input type="button" value="测试按钮" id="btn"></button>
	<div></div>
	<div></div>
	<div></div>
</body>
</html>